Orloj is most visited attraction in Prague. Every tourist who comes to Prague want to see changing of Apostles. The astronomical clock was constructed in 1410 by the clockmaker Mikulas of Kadan in collaboration with Jan Ondrejuv called Sindel, professor of mathematics and astronomy of Prague Charles University. The astrolabe mechanisms were built over 600 years ago and are still functional. the legendary master Hanus rebuild the clock and as legend has it, the Councillors had him blinded, so that he would not ever manage to build another instrument greater than the Orloj in Prague.

Orloj is devided into three parts:
Top: The walk of the apostle ( The Apostles come out of the windows. )
Center: The Sphere or Clock Dial ( It represents the astronomical phenomena such as sunrise and sunset, ancient Czech and present day time, movements of the Sun and the Moon and other relative celestial configurations.)
Bottom: The calendar ( Month symbols are painted by Josef Manes in 1805. The originals of these can be found on the sides of the stairway of the Prague Museum of History.)

12 Apostles:
St. Paul appears first holding a sword and a book
St. Thomas follows carrying a spear
St. Juda Tadeus holds a book in his left hand
St. Simon follows holding a saw being the patron saint of lumberjacks.
St. Bartholomew appears with a book and is the patron saint of tanners, tailors and shoemakers.
St. Barnabas comes last carrying a papyrus.
St. Peter with a key and he is the patron saint to fishermen, locksmiths and clockmakers.
St. Mathew is next with an axe and is the patron saint for builders, carpenters, blacksmiths and butchers.
St. John can be seen castigating a snake being the patron saint of printers and writers
St. Andrew with a cross
St. Philip with another cross and is the patron saint for hatters
St. Jacob with a tool for working flax being the patron saint of linen traders.